As others have mentioned; I wouldn't bother with .Opacity unless you are using values beyond 0 and 1. I believe it will be more clear (and more performant, but I'm speculating) to use .Show and .Hide.
To center a form above the NotifyIcon in the System Try; you might want to just grabbing the mouse position and the screen size. Inside the NotifyIcon_Click event you could do...
Dim xPos As Integer = MousePosition.X
And center your form over that position. It won't technically be perfectly centered over the NotifyIcon - if you click on the left edge, it would be centered over the left edge. You can use .GetWorkingArea on the PrimaryScreen to get the height and position the Y value appropriately.